You may download actual plugin from the link below. Just unzip, copy it into ./plugins directory, activate and enjoy.

Note: to fix another big annoyance with WordPress eliminating line breaks – this is what I use to “create” line breaks that WordPress doesn’t kill. In HTML mode insert this code:

<div style="margin:2em;"><span style="display:none;">-</span></div>

Advantage of this method is that you can regulate size of your “custom line break” by changing value in “margin” CSS tag.

Bonus TIP:
Actually I just found a better way to keep linebreaks: Advanced TinyMCE plugin seems to add lot more features to TinyMCE editor as well as has an option to stop WordPress’s messing up with line breaks.